Updating from 5.5 to 5.6/7 causes a cooking issue with Blueprint_Interaction_Device_C

Geronimo57 · February 21, 2026, 1:20pm

Hi all,

We have a problem that is preventing us from cooking a build and therefore updating our demo.

Since we migrated to 5.5, on trying to cook content, we are greeted with the following error:

UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: begin: stack for UAT
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: === Handled ensure: ===
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error:
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: Ensure condition failed: bCustomPropertyListForPostConstructionInitialized  [File:D:\build\++UE5\Sync\Engine\Source\Runtime\Engine\Private\BlueprintGeneratedClass.cpp] [Line: 1256]
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: Custom Property List Not Initialized for /Game/Blueprints/BP_Interaction_Device.BP_Interaction_Device_C
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: Stack:
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb29c168a9 UnrealEditor-Engine.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb279f4f83 UnrealEditor-Engine.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e370eff UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e37ab8d UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e349ca6 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e38f7f6 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e12f6c2 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e130c68 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2dea4195 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b758 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e15526e UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e12fae8 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e130c68 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2dea5c75 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2dea492c UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2dea42ff UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b758 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b750 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b750 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e15526e UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e12fae8 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e130c68 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2dea4195 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b758 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b750 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e15526e UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e12fae8 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e130c68 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e14fa94 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e12de57 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e130c68 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2dea4195 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b758 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b750 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b750 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e15526e UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e12fae8 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e130c68 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2dea4195 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b758 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b750 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b750 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e15526e UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e12fae8 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e130c68 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2dea4195 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b758 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b750 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e15526e UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e12fae8 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e130c68 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e14fa94 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e12de57 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e130c68 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2dea4195 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b758 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b750 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b750 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e15526e UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e12fae8 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e130c68 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2dea4195 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b758 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b750 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e15526e UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e12fae8 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e130c68 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e14fa94 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e12de57 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e130c68 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2dea4195 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b758 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b750 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e15526e UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e12fae8 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e130c68 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2dea4195 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b758 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b750 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b750 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e15526e UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e12fae8 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e130c68 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2dea4195 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b758 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b750 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e15526e UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e12fae8 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2e130c68 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2dea4195 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b758 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: [Callstack] 0x00007ffb2de7b750 UnrealEditor-CoreUObject.dll!UnknownFunction []
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error:
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: end: stack for UAT

Please note: We don’t even have a BP_Interaction_Device.BP_Interaction_Device_C, just BP_Interaction_Device.BP_Interaction_Device. We’re not sure were the C is coming from.

We’ve noticed others have reported the same issue, and various fixes have been proposed, none of which worked for us. For reference, we have tried the following:

Recompiling the blueprint (no errors flagged)
Clearing the project cache.
Fixing redirectors.
Changing engine version from 5.6 to 5.7.
Someone suggested commenting out a line (FLinkerLoad::DeferExportCreation in BlueprintSupport.cpp) so the assert no longer fires, as suggested in this thread. This also did not work.

We haven’t tried deleting or redoing the blueprint (as its us

BP_Interaction_Device.txt (297.5 KB)

ed extensively in our project), and others have reported doing the same and still encountering the issue.

I have uploaded a text file with the blueprint in question if anyone wants to take a look and investigate.

At this point, we are actively blocked from creating a new build (for demos, etc) until the issue is resolved. Does anyone know what could be the problem here, and what we can do to fix it?

Any help would be greatly appreciated!

brs-sebascova · February 23, 2026, 4:38pm

Hello there @Geronimo57!

Checking through your logs with my peers, the most critical line is the one at the beginning:

UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: Ensure condition failed: bCustomPropertyListForPostConstructionInitialized [File:D:\build++UE5\Sync\Engine\Source\Runtime\Engine\Private\BlueprintGeneratedClass.cpp] [Line: 1256]
UATHelper: Error: Cooking (Windows): LogOutputDevice: Error: Custom Property List Not Initialized for /Game/Blueprints/BP_Interaction_Device.BP_Interaction_Device_C

And the core reason for this, is the fact the project was migrated. UE is trying to package the Interaction Device, finds the compiled class, but the properties inside are either null or corrupted.

In 5.5, the engine would just rebuild the metadata and carry on, but this process became a bit more strict in 5.6 and onwards, stopping the whole thing. So, what we need to try here is to refresh said metadata.

You have already tried recompiling, clearing the cache, and fixing up redirectors. Still, the issue persists. I think there are two more methods to try:

Part of the outdated/corrupted data can affect the BP’s nodes, holding links to pins that no longer exist in your current version. To clear those up, open your BP, go to File, and click on “Refresh All Nodes”. This should force every node to recreate all pins in relation to the current build. After that, recompile and test again.
Duplicate the affected BP, name it something like “BP_Interaction_Device_Alt”. This will create a fresh set of references for the BP, and any old remaining metadata should be ignored. Test a cook with said BP. If it works, you can apply “Replace References” to the old BP.

Geronimo57 · February 26, 2026, 1:45pm

Hi,

Thanks for the reply. This is what I did, and managed to resolve the issue:

I tried migrating the broken blueprint to a new project (and any dependent blueprints) but that also failed the cook with the same error.

However, rebuilding the blueprint from scratch (just creating it again in a new project, same calls, functions, variables, event dispatchers, etc) and making small tweaks to any affected blueprints (refreshing nodes, etc) lead to a successful cook.

This is one solution. I was about to do the same in the original project, but I decided instead to duplicate the blueprint first. I then tried to delete the original one. It had 198 references, and I redirected it to the duplicate, and proceeded.

In most cases, it said some consolidations couldn’t be done, and told me you can try an editor command to ensure affected packages aren’t loaded at start. I ignored this, initially.

The original blueprint always remained, even after I had selected it to be deleted,=.

I noticed that, if you repeated this step each time, the list of affected blueprints would diminish. I did this about 4-5 times until there were only 4-5 blueprints affected.

With the remaining ones, it was just a case of refreshing some nodes, or if that didn’t work, simply recreating them and compiling, and then it worked.

Then I finally force deleted the old blueprint, knowing there were no longer any pending references.

So to summarise:

Duplicate the blueprint.
Delete the old one.
Redirect it to the dupe (it will fail a lot)
Repeat Step 3. The list of dependencies should shorten.
When you keep hitting the same dependencies, manually edit those and refresh node/rebuild the affected calls.
Force delete the old blueprint.

I hope this helps out anyone else that hits this issue.